Viruses

Question 1

What are obligate intracellular parasites

Answer 1

Need cell machinery of host cell to replicate

Question 2

How do envelopes affect the virus

Answer 2

enveloped - sensitive
naked - resistant and more easily transmitted
Helical or icosahedral (closest shape to a sphere so can fit a lot in)

Question 3

How are capsids formed

Answer 3

Self assemble, each subunit has identical bonding contacts with neighbouring proteins.
Symmetrical assemblies of oligomers which are linked by non-covalent bonds (fast assembly, disassembly)

Question 4

What is the capsid for?

Answer 4

Protection for nucleic acid, specific attachment to receptors

Question 5

Describe the FIVE stages of a viral life cycle

Answer 5

1) Attachment - binds to specific receptors (cell tropism)
2) Penetration - found in lipid rafts rich in cholesterol and sphingolipids providing more rigid regions more suitable for attachment
3) Uncoating - if enveloped, fusion with host cells plasma membrane then capsid disassembly releasing into cytosol. If naked, taken in by endocytosis, pH drops then proton pump causes release of virus
4) Replication - needs to replicate nucleic acid, ECLIPSE PHASE. need to be assembled into new visions
5) Maturation - may still be non-infectious, proteolytic cleavage by viral or cellular proteases.
6) Budding - are assembled viruses released, can be through lysis

Question 6

How can the virus spread?

Answer 6

Through apical side of membrane into lumen or through base-lateral side (can’t be targeted by vaccines etc)